Optical system



J. A. MAURElR, JR

.ORTICAL SYSTEM Fild July 2, 1 940 5 Sheets-Sheet l Fl .l'

INVENTOR JOHN A. MHQREE /E. Md

' AGENT 9 J. A. MAURER, JR 7 2,299,024

- OPTICAL SYSEFEM Filed'July 2, 1940 5 Sheets-Sheet 2 mvam-oa vow a.M90252, .12.

J. A. MAURER, JR

OPTICAL SYSTEM Filed July 2, 1940 5 Sheets-Sheet 3 INVENTOR I 006W 4.Mal/051mm Oct. 13,1942. J. MAURER, JR I OPTICAL SYSTEM Filed July 2,1940 5 Sheets-Sheet 4 M a mm T W m a VA. N. N IN fizz. w 4/ Y B Oct. 13,1942. J. A. MAURER, JR 9,

4 OPTICAL SYSTEM Filed July 2, 1940 5 Sheets-Sheet 5 FIG. 1 10.12

FIGJSo. H FI GJSb FL INVENTOR AGENT Patented a. 13, 1942 John A. Maurer,In, New York, N.'Y., assignor, by

mesnc assignments, to J. A. Maurcr, Inc., a corporation of New YorkApplication July 2, 1940, Serial No. 343,617

35 Claims. (01. 179-10033) This invention relates to optical systems forthe photographic recording of electrical impulses on a moving film suchas are used in sound recording, picture transmission, and the like. Moreparticularly, it relates to optical systems of this class which produceimpulse records of constant width but varying intensity. Such recordsare known as variable density records.

The optical systems for variable density recording used in present-daypractice commonly employ either a glow lamp, or a string oscillograph orlight valve. These devices for translating electrical impulses intovibrations of a beam of light-have certain inherent drawbacks which aregenerally known and hence need not be stated here in detail. It hastherefore been proposed to employ, for variable density record ing,optical systems having a mirror oscillograph or similar translatingdevice, and it is an object of the invention to provide an improvedoptical system of this type. r

Another object of the invention is the provision of an optical system ofthis type whichis particularly satisfactory as regards efliciency ofillumination, convenience of adjustment, and ease of manufacture.

Another object of the invention is the provision of an optical system ofthis type by means of which a linear relation between the electricalimmechanical slit. With the use of a mechanical slit, however,difficulties are encountered such as the collection of dust particles onit andthe impossibility of reducing its width beyond a certain limit formechanical reasons. It is therefore an object of the invention toprovide in the optical systems hereinabove referred to means whichperform the function of a mechanical slit without having itsdisadvantages.

Still other objects and advantages ofthe invention include those whichare hereinafterstated or apparent, or which are incidental to directionat right angles to the direction in which the film moves at therecording point, that is, the point at which the optical axis of thesystem strikes the film, and the means forming the line image act onlyin a plane which is at right angles to the line image and extendsthrough the recording point. The optical system furthermore has meansfor forming an image of' said line image, which means act only in thesame plane as the means forming the line image. The optical systemfinally has means for imaging the oscillograph mirror approximately atthe image of the line image, which means act in a plane at right anglesto the first mentioned plane and to' the direction in which the filmmoves at the reof an optical system of this type which may be built.with small physical size and at comparatively little cost.

Another object of the invention is the .provision, in such an opticalsystem, 'of means by which a re-imagery of the recording light source onthe film may be positively excluded.

Another object of the invention is the provision of an optical system ofthis type which may permit its visible adjustment, and 'also visiblemonitoring of the recording of the electrical impulses, in aparticularly convenient and accurate manner. I

Another object of-the invention is the provision, in such an opticalsystem of means for producing a light spot of graded illumination whichare easy and inexpensive to manufacture, and

which are generally more satisfactory than simi-- lar means knownheretofore.

More particularly, however, the object of the invention is to improvethe optical systems for variable density recording which are disclosedin my co-pending applications, Ser. Nos. 343,615 and 343,616, filed onthe same day and assigned to the same assignee as the presentapplication. Those optical systems employ, for the formation of a finalline image, means ,which include a cording point.

Throughout the present specification, the di rection in which the filmmoves at the recording point, and the directions parallel to it, will becalled vertical, and the direction in which the line image of theoscillograph mirror extends,

and the directions parallel to it, will be called horizontal, thehorizontal directions being at right angles to the vertical directions.over, the plane in which the means forming the line image act will becalled the vertical plane, and the plane at right angles to the verticalplane and to the direction in which the ,film moves at the recordingpoint will be called the horizontal plane, the horizontalplane'containing the line designated an incandescent lamp I I.

v is directed by .a suitable condenser lens I2, preferably ofwideaperture, upon the mirror I3 of an oscillograph galvanometer (not shown}or imagery of the mirror. The final line image thus is formed merely byoptical means, and its dimensions hence' can be easily controlled bysuitably choosing such means. Its vertical extension or width inparticular can be. reduced considerably, a very fine final line imagebeing desirable in the photographic recording of electrical impulses.

The invention will be better understood when the following descriptionis considered with the accompanying drawings of certain presentlypreferred embodiments thereof, and its scope will be pointed out in theappended claims.

In the drawings:

Fig, 1 is a diagrammatic perspective view of one embodiment of theinvention,

Fig. 2 is a diagrammatic longitudinal section in the vertical plane ofthe optical system shown in Fig. 1, the optical axis being representedas a straight line and an oscillograph mirror being I represented as' anaperture;

Fig. 3 isa corresponding section in the horizontal plane,

Fig. 4 is an elevation of one element shown in v I Fig. 1 showing thelight spot of graded illumina v tion produced thereon,

Figs. 5 to 7 correspond to Figs. 1 to 3 but for the substitution of acylindrical lens for a spherical lens in front of the oscillographmirror,

A cylindrical lens I5 of short focal length acts on the light fluxproceedings through the optical system after it has been reflected frommirror I3; Cylindrical lens I5 has its cylinder axis horizontal andhence does not act in the horizontal plane. But by its action in thevertical plane cylindrical lens I5 forms at some position A close to ita line image of mirror I3 (see Fig. 2)

A second cylindrical lens I6 is placed between cylindrical lens I5 andthe film II. Cylindrical lens I6 also has its cylinder axis horizontaland therefore also acts in the vertical plane only. Its function is toimage on film II at the recording point I8 the line image of mirror I3which is formed at position A by cylindrical lens I5 (see Fig. 2). Thisdouble imagery of mirror I3 by the two cylindrical lenses I5 and I6,which both act in the vertical plane only, results in.the formation, atthe recording point I8, of a final line image whose vertical extensionor width can be reduced considerably without loss of illumination byselectingcylindrical lenses of suitable Fig. 8 is a diagrammaticperspective view of another embodiment of the invention,

Fig. 9 is a diagrammatic longitudinal section in the vertical plane ofthe optical system shown in Fig. 8, the optical axis being representedas a straight line and an oscillograph mirror being in the verticalplane of the optical system shown in Fig. l, a cylindrical mirror beingsubstituted for a cylindrical lens and a mask having been omitted.

Fig. 16 is a perspective View of a modification of, an element common tothe optical systems shown in Figs. 1 to 3, 5 to 7, and 8 to 10,

Fig. 17 is a perspective view of another modification of the opticalsystems shown in Figsnl to3,5to'7,and8to10,and j Figs. 18a and 18?) showadaptations to a particular purpose of an element common to theoptical-systems shown inFigs. 1 to 3, 5, to I, and 8 to 10. I

Throughout the drawings identical parts are y identical referencecharacters.

Referring first to Figs. 1 to 4, there is shown'a recording light sourcesuch as the filament III of similar device translating electricalimpulses into mechanical vibrations. The axis IlI4 about l horizontally.

heal and horizontal plane's.

optical constants.

A spherical lens I9 is placed between cylindrical lenses I5 and I6 insuch a manner that position A falls within lens IS. The focal length ofspherical lens I9 is so chosen that it forms an image of mirror I3 on,or in the neighborhood 01', film I], that is, approximately at therecording point I8 and the image formed there by cylindrical lens I6. Tothrow the image of mirror I3 slightly out of focus with respect to filmI! has the advantage that the ordinarily coiled structure of lampfilament II, which is reproduced on mirror I3, is not re-imaged on filmII, where it would cause striations of a generally undesirablecharacter.

As lens I9 is spherical it acts in both the ver- By its action in thehorizontal plane, it determines the horizontal extension or length ofthe final line image formed at the recording point I8, which lengthdepends upon the horizontal extension or length of the image of mirrorI3 as produced by spherical lens I9 (see Fig. 3). A

The action of spherical lens I9 in the vertical plane has very littleeffect on the formation of the final line image because the power ofspherical lens I9 in this plane is negligibly small in comparison withthe power of cylindrical lenses I5 and IS in the same plane. The actionof spherical lens I9 in the vertical plane may there-,

fore be barred, and it is actually barred in the optical system underdiscussion by a mask 20 placed in front of cylindrical lens I5 (see Fig.2) Mask 28 is so placed with respect to cylindrical lens I5 that itintercepts the light flux not acted upon by that lens in order to avoidthe forma tion, by'spherical lens I9, of'undesirable secondvary andtertiary images of mirror I3 in the vicinity of the recording point I8(see Fig. 2).

It will thus beseen that by the cooperation of cylindrical lenses I5 andI 6 andsphericallens I9 there is formed at the recording point I8 afinal line image whose width and length are de- I 'fined by therespective actions of these lenses.

The amount of light present in the final line im- Light from filament I0age, however, is varied in accordance with the electrical im'pulses tobe recorded as follows:'

A screen 2| is placed between lamp II and mirror I3 and adjacent 'tocondenser lens I2. Screen ZI has .an opening 22 which is an isoscelestriangle with its base extending horizontally, and which isuniformly-illuminated by lamp filament I0. Thus, there is formed atscreen 2| a uniformly illuminated light spot whose horizontal extensiongradually varies in a vertical direction.

v A cylindrical lens 23 with its cylinder axis horizontal is placed infront of mirror I3. Cylindrical lens 23 forms an image of opening 22 on,or in the neighborhood of, mask 20, that is," approximately atcylindrical lens I (see Fig. 2).

only, the image of opening 22 is a light spot 24 (see Fig. 4) whoseillumination gradually varies whose horizontal extension graduallyvaries in a a vertical direction by a cylindrical lens acting in thevertical plane only, and also of the aperture effect of a'small mirrorupon such imagery, reference is made to my application Ser. No. 343,616.

From which horizontal level of light spot 24 the light flux emanateswhich is acted upon by cylindrical lens I5 depends upon the degree ofdeflection of mirror I3, as light spot 24 is vertically movable by thevibration of mirror I3 about its horizontal axis" 14-. When thereforethe electrical impulses to be recorded are applied in known manner tothe oscillograph galvanometer on which mirror I3 is mounted, the lightflux contained in the line image of mirror I3 as formed by cylindricallens iii-varies in accordance with the electrical impulses to berecorded and in a manner which is directly and linearly proportional tothe manner in which the horizontal extension of opening 22 graduallyvaries in a vertical direction.

'I'hesevariations of the light flux contained in the line image ofmirror l3. formed at position A become manifest as variations of itslength as well as of its illumination, because the uneven distributionas regards length and intensity of the light flux containedin light spot24 is not 1 altered at position A since position A is close to lightspot 24 and cylindrical lens I5 does not.

act in the horizontal plane. But in the final line image formed at therecording point I8, they become manifest only as variations of itsillumination, for the length of the final line image is determined bythe length of the image of mirror I3 formed by the action of sphericallens I9 in the horizontal plane, and this image length remains constantno-matter into what position mirror I3 is deflected, provided, ofcourse, that at least some part of the light flux contained in lightspot 24 enters cylindrical lenses I5 and Hi. The length of the image' ofmirror I3 as formed by spherical lens I9 should therefore be at leastequal to the desired horizontal extension or width of the impulse recordon film I'I.

The action of spherical lens I9 in the horizon-- tal plane furthermorebrings it about that whatever light flux is contained in the line imageformed at position A is evenly distributed over the length of the'finalline image, although it was not evenly distributed horizontally in theline image formed at position A.

Thus a final line image whose length is constem and whose illuminationvaries in accordance with the electrical impulses to be recorded, isformed at the recording point I8, and a variable density record isproduced ,on film I! when it moves past the recording point I8 in asubstantially vertical direction, as indicated by the arrow 25.

In Figs. 5 to '7 and 8 to 10, there are shown by way of further exampletwo other optical systems embodying the present invention. As in thecase shown in Figs. 1 to 4, the width of the final line image formed atthe recording point I8 is determined also in these two cases by theimage of mirror I3 as formed by the actions of cylindrical-lenses I5 andI6 in the vertical plane only, and its length by the image of mirror I3as formed by the action of sphericallens IS in the horizontal plane. Butthe two cases diifer fromeach other and from the case shown in Figs. 1to 4 in the manner in which the amount of light present in the finalline image is varied in accordance with the electrical impulses to berecorded.

zontal extension gradually varies in a vertical In other words, thelight direction (see Fig. 5). flux contained in light spot 21 now isevenly distributed over horizontal levels of light whose lengths, andtherefore the light flux contained therein, gradually vary in a mannerwhich is directly and linearly proportional to the manner in which thehorizontal extension of opening 22 gradually varies in a verticaldirection.

As light spot 2l again is vertically movable by the vibration of mirrorI3, what part of the light flux evenly-distributed in light spot 21 isacted upon by cylindrical. lens I5 depends upon the degrees ofdeflection of mirror I3 in such a manner that, for varying degrees ofdeflection,

by cylindrical lens I5 at position A. In the final line image formed atthe recording point I8, however, they again become manifest only asvariations of its illumination, because its length is again determinedby the constant length of the image of mirror I3 formed by the action ofspherical lens I9 in the horizontal plane.

The case shown in Figs. 8 to 10 also employs spherical lens 26 forimaging, by its action in both the vertical and horizontal planes, theuniformly illuminated opening in screen 2I approximately at cylindricallens I5. But opening 28 in screen 2| now is a rectangle with one of itssides extending vertically, and the axis 29-29 about which mirror 13 ismounted to vibrate now extends vertically. The image of opening 28 is alight spot 30 whichagain is uniformly illuminated, but which now ishorizontally movable by the vibration of mirror I3. Thus, more orless ofthe evenly distributed light flux in light spot cordance with theelectrical impulses to be recorded. For the reason stated in connectionwith .the'case shown in Figs. to 7, the variations in light flux oftheline'image formed by cylindrical lens l5 at position A again; becomemanifest substantially as variations of the length of this line image,while the corresponding variations inlight fiux of the final line imageof constant length again become manifest asvariations of only itsillumination.

It is understood that the vibration of mirror ll about the vertical axis29-29 effects changes I of the length of its image as formed by theaction of spherical lens I! in the horizontal plane.

. 2,299,024 at is permitted to enter cylindrical lens is in 9.0-

the result of varying the light flux contained in the line image ofmirror l3 formed at position A, it being understood that the image ofthe opening, and the line image of mirror l2 formed by cylindrical lensl5, must be properly dimensioned in order to permit the degree ofvariation desired.

. Hence, with an opening of-suitable shape the mirror I! formed byspherical lens I! remains constant also when mirror l3 'vibrates about avertical axis.

The different means employed in the three optical systems shown in Figs.1 to 4, 5 to '7, and 8 to 10 for varying the amount of light present inthe final line image, are alike in that in each case they include anopening which is uniformly illuminated by lamp filament'lfl, that is,means forming a uniformly illuminated light spot, and means acting inthe vertical plane for forming an image of this light spot approximatelyat cylindrical lens IS, the image of the light spot being movable by thevibration of mirror H. The action of the last mentioned means in thehorizontal plane is immaterial as far as the formation of the final lineimage is concerned. This action in the horizontal plane therefore isrequired only in the case shown in Figs. 8 to 10, wherein the light fluxcontained in the image of the uniformly illuminated light spot mustsubstantially be evenly distributed horizontally 'because this image ishorizontally movable by the vibration of mirror l2.

The fact that in the two cases shown in Figs.

1 to 4 and 5 to 7 there may be employed, for

the imagery of opening 22,,either cylindricallens 23 or spherical lens28 aifords an advantageousdegree of freedom in designing a particularoptical system in accordance with the present invention. The employmentof cylindrical lens 22,

however, has the specific advantage that reimagery of the structure oflamp filament It on film I1 is excluded for any working position ofmirror l3, this being the case under the provision and--for the reasonstated in my application Ser.

110,343,616. The employment of spherical lens 28, in its turn, permits,on account of the formation of a uniformly illuminated lightspot on,'orin the neighborhood of, mask 20, visible adjustment of the opticalsystemshown in Figs. 5 to '7,

and also visible. monitoring of the recording of I the electricalimpulses, in a particularly convenient and accurate manner.

On the other hand, the two cases shown in Figs. 5 to '7 and 8 to 10'both employ spherical lens 26 for the imagery of the uniformlyilluminated light'spot formed at screen 2|. The

image of this light spot has to be vibrated in different directions inthe two cases, the respective direction depending upon the shape of the.

exclude its image, when formed by spherical lens 26, from being vibratedin some direction with axis of vibration of mirrow l3 need neither behorizontal as is axisl4--|l, shown in Fig. 1, nor vertical as is ,axis29-49, shown in Fig. 8, but may have any inclination with respect to thevertical and horizontal planes of the optical system which it is founddesirable to have in a particular case.

The optical systems shown in Figs. 1 to 4, 5 to 7, and 8 to 10 of thepresent specification are capable of the following modifications whichmay be applied to each of them unless stated otherwise:

(1) Opening 22 in screen 2| is shown in Figs. 1 and 5 as being anisosceles triangle. However, with mirror l3 vibrating about a horizontalaxis. screen 2| may have any other opening whose horizontal extensiongradually varies in a vertical direction, such an opening having atleast one edge which is inclined with respect to the horizontal plane ofthe optical system. The opening in screen 2| may, for example, be aright-angled triangle 35 with one of the sides adjacent to the rightangle extending horizontally as shown in Fig. 11, or there may be one ormore saw-tooth projections extending into it as they do into openings 3iand 31 in Figs. 12 and 13.

If any of the openings shown in Figs. 11 to 13 is imaged by cylindricallens 23, there is formed approximately at cylindrical lens IS a lightspot whose illumination gradually varies in a vertical direction, forcylindrical lens 22 does not 'act in the horizontal plane. The verticaldisplacement of this light spot ofgraded illumination by the vibrationof mirror ll produces variations in light flux of the iine'image oimirror l3 formed at position A, which variations become manifest, as

- as variations in illumination of this line image.

If, on the'other hand, the images of the openings shown in Figs. 11 to13 are formed by spherical lens 26 and moved vertically by the vibrationof mirror II, the variationsin light fiux of the line image formed atposition A become manifest substantially as variations of its length.While, however, with opening 22 (Fig. 5) the line image of mirror l3varies in length at both its'ends, it

does so at only one end with opening 35 (Fig. 11). With opening I. (Fig.12), there are formed two line images in iuxtapomtion, each varying inlength at only one of its ends, and with opening 21 (Fig. 13) aplurality of line images, likewise in juxtapositionbut each varying inlength at both its ends. But because cylindrical lens l6, which imagesthis line image or images at the recording point l8, does not act in thehorizontal plane, there is formed in any of these cases at the recordingpoint I! a single final line image whose illumination varies when theline image or images formed at position A vary in length.

The gradual variation of the light flux contained in the line imageformed at position A is produced by the vibration of mirropri 3 inaccordance with the electrical impulses to be recorded. The character ofthis gradual variation, however,

' depends in each of the two cases shown in Figs. 1

to 4 and 5 to 7, respectively, only upon the gradual variation, in avertical direction, of the horion the reflected light flux,

lindrical .lens l could produced by the inclined edge or edges thereof.The lower portion of screen 2| may therefore be omitted if desired asindicated by way of example by the broken line 38-38 m Fig. 11.

In order to effect a linear relation between the electrical impulses tobe recorded and the transparency of the record used for theirreproduction, the horizontal extension of the opening in screen 2| maygradually vary in a non-linear manner. To that end, one or more of itsinclined edges may be curved as are the two inclined edges of opening39, shown in Fig. 14, a method of computing a suitable curve beingdisclosed, for example, in British specification 424,042 (I. G.Farbenindustrie). Thus, distortions may be canceled which areintroduced, for example, by the non-linear characteristics of theoscillograph galvanometer on which mirror i3 is mounted, or of theemulsions of the recording and, printing films, or both.

(2) Screen 2| when used in conjunction with a mirror vibrating about avertical axis need not have a rectangular opening such as opening 28shown in Fig. 8. It may have any other opening permitting the formation,approximately at cylindrical lens 35, of an image thereof by sphericallens 26, as long as this image has an edge by the horizontaldisplacement of which the line image formed at position A is varied inlength at one of its ends. Such an edge need .not be straight as is edge40, shown in Fig. 8, but may be curved or even ragged if desired.

(3) While cylindrical lens 23 and spherical lens 26, respectively, areshown as being placed in front of mirror I3 so as to act on the lightflux proceeding through the optical system both before. and after it isreflected from mirror l3, they may also be placed so that they act ononly the incident or only the reflected light flux.

Instead of spherical lens 26" theremay also be used in the cases shownin Figs. 5 to '7 and 8 to 10, respectively, two cylindrical lenses oneof which may act on the incident and the other the opening in screen 2|being imaged approximately at cylindrical lens l5 by one cylindrical lenacting. in the vertical and by the other acting in the horizontal plane.

The image of th opening in screen 2| has been described hereinabove asbeing formed by cylindrical lensv 23, and spherical lens 26 or itssubstitutes, respectively, on, or in the neighborhood of mask 20, thatis, approximately at cylindrical lens l5. This expression is not-meantto exclude the possibility that this image is formed back of cylindricallens l5, instead of in front of it as shown, by way of example only, inFigs. 1 to 4, 5to7,and8toi0. a

in substance age of mirror l3 as formed by a concave cylindrical lens ora convex cylindrical mirror. (5) While mask 20 is shown as being placedin front of cylindrical lens l5, it may also have any other positionbetween mirror l3 and film H where it intercepts the light flux notacted upon by cylindrical lens l5. In an actual optical system designedaccording to the present invention, however, this function of mask 20may be performed by the means lens l5 in its place in the opticalsystem. The provision of a part specifically embodying mask 20 isequally superfluous in an actual design when cylindrical mirror isemployed in place ,of cylindrical lens l5. All that need be done in..this case is to blacken the parts of the housing structure Mask 2|) hastherefore been omitted from Fig. 15, which shows the employment ofcylindrical 'mir-, ror A5.

(6) It has been pointed out hereinabove that h it is immaterial-that theaction of spherical lens IS in the vertical plane is barred by mask 20.Hence, there may be used in place of spherical lens ii! a cylindricallens 89 with its cylinder axis vertical, as shown in Fig. 16, lens t9having the same focal length and aperture as lens i9 but acting in thehorizontal plane only. On the other hand, no harm will result if, inembodiments of the invention other than those shown and described in thepresent specification, spheri- .screen 2| by cylindrical lens 50 lens26.

(4) Cylindrical lens l5 may be replaced b a cylindrical mirror 45, asshown byway of example in Fig. 15 for the case shown in Figs. 1- to 4.From Fig. 15, whih is a section in the vertical plane, it will be seenthat the employment. of cylindrical mirror 45 affords the specificadvantage that the optical system may be folded in a convenient mannerwithout the use of additional prisms or like means for-altering thedirection of alightbeam. Y Q

Cylindrical mirror 45 is shown asbeing concave in Fig. 15, andcylindricallens l5 as being convex throughout the drawings. However,cyalso be concavegand cylindrical' mirror 45 convex,

hereinabove with respect to the real image of the explanation given asthe reflected light flux,

shown in this position. by

cal lens I!) should image mirror l3 by acting in the vertical planealso.

Spherical lens l9 has been shown and de-- being placed between cy- IS insuch a manner that scribed hereinabove as lindrical lenses l5 andvposition A falls therewithin. 'Spherical lens I! may, however, have anyother positionbetween cylindrical lenses l5 and I6 which is consistentwith its function to image, by its action in the horizontal plane,mirror l3 approximately at the recording 'point I8. As long as isfulfilled, spherical lens l9 may also be placed between mirror l3 andcylindrical lens I5, and preferably in the immediate vicinity of lens l5so as not to interfere, by its action in the vertical plane, with theimagery of the opening in 23 or spherical When cylindrical ed-out in thepreceding paragraph for spherical lens i9. As, however, cylindrical lens49 does not act in the vertical plane, placed between mirror l3 andcylindrical lens I5 is less critical than is that of spherical lens l9.

When the optical systems disclosed in the presentspecification employspherical lens l9 and cylindrical lens 49, respectively, may be placedin front of mirror 45 in such a manner as to act on the incident a wellway of example, in

Fig, 1 ('7) and described hereinabove as being formed immirror l3 asformed by a convex cylindricallens or a concave cylindrical mirrorbeing. applicable mediately on film It may, however, also be re-imagedon film at a convenient place between cylindrical lens also with respectto the virtual iniholding cylindrical which surround mirror 45.

this condition lens is employed to image a mirror 3 approximately at therecording point x it, it may be placed in any of the positionspointits'position when cylindrical mirror 45,

spherical lens I!) being The final line image of constant lengthproduced by H by suitable means inserted commonly. practised I6 and mmII, which means may act'in the vertical and horizontal planes eitherwith or withoutchanging, in either one plane or in the two planes,image.

(8) It has been assumed hereinbefore that the final line image formed atthe recording point I 18 is or uniform illumination throughout its enthedimensions of the final line both the present specification are soadjusted that in v the rest' or zero position of mirror 13, that is,

' -when no electrical impulses are applied to the oscillographgalvanometer on which it is mounted, the line image of mirror l3 'formed at position contains about half the light flux" present therein whenit has its maximum length and illu- 'min'ation. -If, however, sound isto be recorded tire length; Actually, this is true only in case theimage oi, mirror 13. formed by'spherical'lens '19 or cylindrical lens 49is in focus at the re-.

cording point l8. If it is out of focus with respect thereto theillumination of the final line image decreases at its ends, and only itscentral portion ispuniformly illuminated. The edges 01' the impulserecord are therefore blurred in this case and should be screened ofiwhen prints of the record are made, such screening of! now being inprinting from variable de ity r ords.

If, however, it desired to eliminatethe blurred edges when making theoriginal record on film I1, two screens ing vertical ed'g'fes lil' and68 may be employed,

sand 68 'or likemeans havedges .61. and t8 being spaced apart'so as toconfine between themselves the uniformly illuminatedlcentral portion ofthefinal line image.

Screens .65 i and 66 may -be placed between cylindrical' lens IE andfilm 11, as shown in Fig. '15,or in front of lamp l l 'ormirror l3.

9) The optical-systems disclosed inthe present specification'arecharacterized by the fact final stage a lens 116' which acts in thevertical plane only. 'Lens; l6 therefore has to be cylindrical, and-therequired employmentof .a cylindrical short focal length. which permitsof building the optical systems with small physical size, and acylindrical lens -of;short focal length is less expensive than aspherical lens system well enough by the method generally known asnoiseless recording, mirror may be biased in the manner disclosed in L.T. Robinsons U. S. specification Alternatively, screen 2| may bevibrated vertically when employed with the optical systems shown inFigs. 1 to 4 and 5 to 7., respectively, of

the present specification, or horizontally when employed with theoptical system shown in Figs.

8- to 10 thereof. To that end, it may be connected by'a' stem 10, inFigs. 18d-and 18b, or like means, to a motor to which an electriccurrent corresponding to the envelope of the sound waves to be recordedis 36' shown in Fig. Fig. 14, or a similar opening, noiseless recordingapplied. Such a motor and a method ion-its operation is disclosed, forexample, in H. McDowell,

-' Jr.s, U.S specification 1,855,197.

Finally, when screen 2| employed with the optical systems shown in Figs.1 to 4 and'5 to 7, respectively, of the present specification, has theopening 22v shown in Figs. 1 and 5, the opening 12, theopening 39 shownin may also be achieved by providing adjacent to that, for imaging atthe recording point 18 the -line image of 'mirror I 3, there is employedin their lens in the final stagelof the optical systems has inherent'advantages: Such a lens may .have acorrected to be capable'of forming,over the same length, an equally-sharp line image. The optical systemsmay-therefore be built at comparatively little cost.

,(10) 'The method for determining the dimer!- sions 'of the final lineimage which is disclosed in the present specification, consists inimaging mirror 13 successively by two means acting in the vertical planeonly and also imaging it by means acting'in the horizontal plane. Thismethod may for varying-the amount of light present'in the final lineimage which are described hereinabove by way of example, but also withother-means for accomplishing the same end provided that they include anoscillograph mirror. Such other means are disclosed, for example. in G.L. Dimmicks U. S. Specifications 2,095,317 and 2,095,-

318, in which it has been proposed to form a penumbra whose gradationprogresses vertically, and which is movable by the vibration of anoscillograph mirror about a horizontalaxis It, for example, suchapenumbra is formed in the optical system shown in Figs. 1 to 3 ofthemesent specification, approximately at cylindrical lens IS, thevariation-0f the amount of light present in the final line imageresulting from the .vibration of the penumbra by mirror 13 is .thesame-as that produced by the vibration of light spot 24 formed in thisoptical system by the imagery of opening 22 by cylindrical lens 23.

(11) Normally, the optical systems disclosed in be employed not onlywith the particularmeans screen 2| a twin shutter mechanism similar tothat disclosed in H. J. Hasbroucks U. S. specification 2,102,778.

The application of any of the methods for noiseless recording mentionedabove will result in'shiiting the mean density of the soundprod'uced'on'film H in accordance with the en- .v'elope of the soundwaves to be recorded,

Many other'modifications of the invention will readily suggestthemselves to those skilled in the art. The invention, therefore, is notto b limited, except in so far as is necessitated by the prior art andby the spirit of the appended claims.

a mirror adapted to vibrate in accordance with -'sald electricalimpulse,

cylindrical lens with its cylinder axis horizontal i for forming at someposition 'close thereto a line the combination of a image of saidmirror, means acting in the vertical plane only for forming an image ofsaid line image, and means acting in the horizontal plane for imagingsaid mirror approximately at-said,

image-ot'said line.

3. In an optical, systemfor the photographic recording of electricalimpulses which includes a mirror adapted to vibrate in accordance withsaid electrical impulses, the combination of a cylindrical lens with itsfor forming at some image of said mirror,

cylinder axis horizontal position close thereto a line shown by way ofexample thereto a line image I means acting in the vertical axisvertical for imaging said mirror approximately at said image of saidline.

4. In an optical system for the photographic recording of electricalimpulses which includes a mirror adapted to vibrate in accordance withsaid electrical impulses, the combination of a cylindrical mirror withits cylinder axis horizontal for forming at some position close theretoa line imag of said mirror, means acting in the vertical plane only forforming an image of said line image, and means acting in the horizontalplane for imaging said mirror approximately at said image of said line.

5. In an optical system for the photographic recording of electricalimpulses which includes'a mirror adapted to vibrate in accordanc withsaid electrical impulses, the combination of a cylindrical mirror withits cylinder axis horizontal for forming at some position close theretoa line image of said mirror, means acting in the vertical plane only forforming an image of said line image and a cylindrical lens with itscylinder axis vertical for imaging said mirror approximately at saidimage of said line.

6. In an optical system for the photographic recording of electricalimpulses which includes a mirror adapted to vibrate in accordance withsaid electrical impulses, the combination of means acting in thevertical plane only for form- V ing at some position close thereto alineimage of said mirror, means forming a uniformly illuminated lightspot, means acting in the vertical plane for forming an image of saidlight spot approximately at said first mentioned means, said luminatedlight spot, means acting in the vertical plane for forming an image ofsaid light spot approximately at said first mentioned means, said imageof said light" spot beingmovable by the vibration of said mirror, meansacting in the vertical plane only for forming an image of said lineimage, and means acting in the horizontal plane for imaging said mirrorapproximately at said image of said line.

- 10. In an optical system for the photographic recording of electricalimpulses the combination of a light source, a mirror adapted to vibratein accordance with said electrical impulses,

movable by the vibration of said mirror, and a means acting in thevertical plane only for forming an image of said line image.

7 11.- An optical system for the photographic recording of electricalimpulses on a film which moves at the recording point in a substantiallyvertical direction, having, in combination, a

light source, a mirror adapted to vibrate in ac- 4 cordance with saidelectrical impulses, means for directing light from said light sourceupon said mirror, means acting in the vertical plane only for forming atsome position close thereto a said electrical impulses,ithe combinationof a cylindrical lens with its cylinder axis horizontal for forming atsome position close thereto a line image of said mirror, means forming auniformly illuimanted light spot, means acting in light spotapproximately at said cylindrical lens,

- said image-of" said light spot being movable by the vibration of saidmirror,- and means acting in. the vertical plane only for forming animage of said line image.

8, In an optical system' for the photographic recording of electricalimpulseswhich includes mirror, said image of said light spot beingmovable by the vibration of said mirror, and means acting in thevertical plane only for'formirigan image or s'aid'line image.

9. In an optical system for the photographic recordingof electricalimpulses which includes a mirror' adapted to vibrate in accordance with,said electrical impulses, the combination of ,the'vertic'al plane forforming an image of said means acting in the vertical plane only forforming at some position close thereto a line image of said mirror,;meansforming 'a uniformly il line image of said mirror, a screen with anopening, said opening being uniformly illuminated by said light source,means acting in the vertical plane for forming an image of said openingap proximately, at, said 1 second mentioned means,

said image of said opening, being movable by the vibration of saidmirror, means acting in the vertical plane only for forming ant image ofsaid line image at said recording point, and means between said mirrorand said film' for intercepting the ,light flux not acted upon by saidsecond mentioned means. v

12. An optical system for the photographic recording of electricalimpulses on. a film which moves at the recording point in asubstantially vertical direction, having, in combination, a lightsource, a mirror adapted to vibrate 'in accordance with said electricalimpulses,

means for directing light fromsaid light source upon said mirror, meansacting in the vertical plane OHIYFfO'I forming at some position closethereto a line image of said mirror, a screen with an opening, saidopeningbeing'uniformly illuminated by said light source; means acting inthe vertical plane-for forming an image or said opening approximately atsaid second mentioned means,.said imagefof said opening being movableby, the vibration of said mirror, 'mean's acting'in-the vertical planeonly for forming an image of. said line image at said recording point,means between said mirror and said film tor-in tercepting the light fluxnot acted upon by said second mentioned means, and means acting in thehorizontal plane. ror imaging said mirror approximately at saidrecording point.

, 13. In an optical system for thephotographic recording of electricalimpulses which includes 7 a mirror adapted to-vibrate about a horizontalaxisin accordance with said'electrical impulses,

the combination of means acting in the vertical plane only for; formingat some-position close thereto a line image of said mirror, meansforming a uniformly illuminated light spot the horizontal extension ofwhich gradually varies in a vertical direction, means acting in-thevertical plane for forming an image of said light spot approximately atsaid first mentioned means, said image of said light spot being movableby the vibration of said mirror, and means acting in the vertical planeonly for forming an image of said line image. a V

14. An optical system as defined in claim 13 Y wherein the horizontalextension of said light spot gradually varies in a vertical directionand in a non-linear manner so as to effect a linear, relation betweensaid electrical impulses and the transparency of the'record used for thereproduction thereof.

15. In an optical system for the photographic recording of electricalimpulses the combination of a light source, a mirror adapted to vibrateabout a horizontal axis inaccordance with said electrical impulses,means for directing light from said light. source upon said mirror,means acting in the vertical plane only for forming at somepositionclose thereto a line image of said mirror,

' a screen with an opening the horizontal extension of a. light sourcera mi iadapted it time: about a horizontal axis in accordance with said.

electrical impulses, means for light from said light source upon saidmirror, mean'sacting inthe vertical plane only for forming at someposition close thereto a line image of said mirror; a screen with anopening which is a right-angled triangle with one of-the sides adjacentto the right angle extending horizontally, said opening being uniformlyilluminated b'y said light. source,

means acting in the vertical plane for forming only for iormingan imageof said line image. l

of which gradually varies in a vertical direction,

said opening being uniformly illuminated by said light source, meansacting. in the vertical plane for forming an image of said openingapproximately. at said second mentioned means, said 7 image of saidopening being movable by the vibration of said mirror, and means actingin the vertical plane only for forming an image of ,said

line image.

16. An optical system as defined in claim 15 wherein said screen isvertically movable in accordance with the envelope of said electricalimpulses. v

17. In an optical system for the photographic recording of electricalimpulses the combination of a light source, a mirror adapted to vibrateabout a horizontal axis in accordance with said electrical impulses,means for directing light 22. An optical system as defined in claim 21.wherein the inclined side of said right-angled trlv angle is curved soasto eflectalinear' relation cordance with the envelope "of saidelectrical- 24. In an optical system recording of electrical impulseswhich includes a mirror adapted to vibrate about a horizontal ads I inaccordance with said electricalimpulses, the

combination of means acting in the vertical plane only for forming atsome position close. thereto a line image of said mirror, means formingalunlformly illuminated light spot the horizontal 'ex- I I, tension ofwhichgradu'ally varies in a vertical .direction, means acting in thevertical plane only for forming an image of saidiight spot approximatelyat said first mentioned means, said image of said light spot beingmovable'by the vibration of said mirror, and means acting in thevertical about a horizontal axis in accordance with said electricalimpulses, means for directing light from said light source upon saidmirror, means acting vin the vertical plane only for forming at someposition close thereto a line image of said mirror,

' av screen with an opening the horizontal extension for forming animage of 18. An optical system as d'eflned in claim 17 wherein one ofthe two inclined sides of said isosceles triangle is curved so as toeiiecta linear relation between said electrical impulses and thetransparency of 1 the record used for the reproduction thereof.

19. An optical system as defined in claim 17 wherein the two inclinedsides of said isosceles triangle are curved so as to eflect a linearrelation between said electrical impulses and the transparency of therecord used for the reproduction thereof.

20. An optical system as defined in claim 17 wherein said screen isvertically movable in ac cordance with the envelope of said electricalimpulses.

21. In an optical system for the photographic recording of electricalimpulses the combination tical plane only for forming an image of saidof which gradually varies in a vertical direction, said'opening beinguniformly illuminated by said light source, means acting in the verticalplane only for forming an image of said opening approximately at saidsecond mentioned means, said image of said opening being movable by thevibration of said. mirror, and means acting in the vertical plane onlyfor forming an image of saidline image.

26. In an optical systemfor the, photographic recording of electricalimpulses the combination ofa light source, a mirror adapted to vibrateabout a horizontal axis inaccordance with said electrical impulses,means for directing light from said light source upon said mirror, meansacting in the vertical plane only for forming at some position closethereto a line image of said mirror, a screen with an opening which isan isosceles triangle with its base extending horizontally, said openingbeing uniformly illuminated by said light source, means acting in theveropening approximately at said second mentioned means. said image ofsaid opening being movdefined in claim 21 wherein said screen isvertically movable-mac for the I photographic some position closethereto thereto a line image of said ing' a uniformly illuminated lightspot the horivertical direction, tical only for forming an image someposition close only for termini able-.by the vibration of said mirror;and means acting'in the vertical plane only for forming an image of saidline image.

2'7. In an optical system recording of electrical impulses thecombination of a light source, a mirror adapted to-vibrate about ahorizontal axis in accordance with said electrical impulses, means -ordirecting light from said light source upon said mirror, means acting inthe vertical plane only for forming at a line image of said mirror, ascreen with an opening which is a right-angled triangle with one of thesides adjacent to the right angle extending horizontally, said openingbeing uniformly illuminated by said light source, meansacting in thevertical plane only for forming an image of said opening approximatelyat said second mentioned means,

said image of said opening being movable by the vibration'of saidmirror, andmeans acting in the vertical plane only for forming an imageof said line image.

28. In an optical system for the photographic recording of electricalimpulses which includes a 'mirror adapted to vibrate about a horizontalaxis in accordance with saidelectrical impulses,

the combination or means acting in the vertical plane only for formingat some position close mirror, means formzontal extension of whichgradually varies in a d and .horizontal planes for forming an image ofsaid light spot approximately at said first -mentioned means, said imageof said light spot bein movable by the vibration of said mirror, andmeans acting in the vertical plane of said line image.

29. In an optical system for the photographic recording of electricalimpulses the combination of. a light-source, a mirror adapted to vibrateabout a horizontal axis in accordance with said electrical impulses,means from said light source upon said mirror, means for directing lightacting in the-vertical plane only for forming at some position closethereto a line image of said mirror, a. screen with an opening thehorizontal extension of which gradually varies in a vertical direction,said opening being uniformly illuminated by said light source, meansacting in both the verticaland horizontal planes for forming an image ofsaid opening approximately at said second mentioned means, said image ofsaid opening beingmovable by the vibration of said mirror, and meansacting in the vertical plane only for'forming an image of said lineimage.

- 30: In an optical system for the photographic recording of electrical1 of a light soprce, a mirroradapted to vibrate I about a; horizontalaxis in accordance with said directing light electrical impulses, meansfor from said light source upon said mirror, means acting in thevertical lane only for tor-mine at thereto a mirror, a screen. with anopening which is an isosceles triangle with its base extendinghoriimpulses the combination line image or said for the photographicsome position close thereto a line image of said mirror, a screen withan opening which is a right-angled triangle with one of the sidesadj'acent to theright angle extending horizontally, said opening beinguniformly illuminated by said light'source', means acting in both thevertical and horizontal .planes for forming an image of said openingapproximatelyat said second mentioned means, said image of said openingbeing movable by the vibration of said mirror,

means acting in both the verand means acting in the vertical plane onlyfor forming an image of said line image.

32. In an optical system for the photographic recording or electricalimpulses which includes a mirror adapted to vibrate about a verticalaxis in accordance with said electrical impulses, the

combination of means acting in the vertical plane only for forming atsome position close thereto a line image of said mirror, means forming auni- ,formly illuminated light spot, means acting in both the verticaland horizontal planes for forming an image of said light spotapproximately at said first mentioned means, said image of said lightspot being movable by'the vibration of said mirror, and means acting inthe vertical plane only for forming an image of said line image.v

33. In an optical system for the photographic recording ofelectrical-impulses the combination of a light source, 'a mirror adaptedto vibrate about a vertical axis in accordance with saidelectricalimpulses, means for directing light from said light sourceupon said mirror, means acting in the vertical plane only for forming atsome position close thereto aline image of said mirror,

a screen with an opening, said opening being unimatch at said secondmentioned means, said zontally, said openingbeing un'itormly-illuminatedby said light source. means acting in both the'vertical' andhorizontal planes for formingan image of said opening 'approximately atsaid second. mentioned ,means opening being movable by the vibration orsaid means ai -image oi said line image.

mirror, and

said image of saidv acting in the vertical Planev 'a screenwith'an-openin which is -with oneof its sides extending vertically, saidhorizontal v I opening approximately at said second mentioned means.said image of said opening being movable by the vibration of saidmirror, and means acting in the vertical plane only for forming an imageof said line image.

34. An optical system as defined in claim 33 wherein said screen ishorizontally movable-in accordance with the envelope of said electricalimpulses I '35; In an optical system for the photographic recording ofelectrical impulses the combination of a light source, a mirror adaptedto vibrate about a vertical axis in accordance with said elec-- tricalimpulses, said light source upon said mirror, means acting only forforming at some position close thereto a line image of said mirror, arectangle being uniformly illuminated'by said light means acting in boththevertical and .planes' for, forming an image of said opening source,

imageof said opening being movable by the vibration oi! said mirror, andmeans acting in the vertical Plane only foriorming an image of said lineimage.

1 JHNA JR.

means for directing light from line lpQfqrdegrees" read "degree"; page lgegdndpolmn', line 8:, $9

miimow." read'-v-.-m1i-roi---; page 6, sohd cqlumn', lilies 57 {ix 16,68and pa'ge 7, firt c o11 nnn,1lingas 11., 15 and 26; claims 11:9 5inclusive; a fter the word Fli'n'qfiand before the peridd insert --imageand second coiliu niaf line 1+0, c 1a.i.m 11, strike out'th ecqnnniaftrf'ope ningfiiand yhat th e saiid.

Letters .Patent shuld be egd with m a'corr cpion tn repimhtjmnq a e.

may confgm to 1:215 r ec qrd q: the cage in the patent Offic' e.

A Signed and sealed this 5th day :of January; A. D. 1911.3. i

- (8681) Acting Cbinmissiorir of Paten ts,

